1. Field of the Invention
The field of the invention relates to aquaculture and mariculture systems and more particularly relates to an improved method and apparatus for raising and harvesting fish in an offshore environment wherein a relatively soft seabed of mud exists. The present invention further relates to an improved method and apparatus for raising fish adjacent an offshore platform wherein at least one and preferably a plurality of opposed diagonal support guy wires extend between the platform and an undersea anchor pile, wherein individual fish pens or cages can be quickly transported along the diagonal guy wires with a winch line (eg. an endless winch driven cable) aided by ballast tanks on the cages. Even more particularly, air and food are transmitted to the cages via flexible flow lines that travel with the cages as they move into selected undersea depths, such as to avoid storms and undesirable water quality zones.
2. General Background
In the Gulf of Mexico, excellent conditions exist for raising many species of saltwater fish in an aquaculture or mariculture environment. However, the Gulf of Mexico experiences drastic changes in both weather conditions and in water quality.
One of the common problems with water quality in the Gulf of Mexico is the presence of hypoxic (low dissolved oxygen) or "dead zones" that are not suitable for aquatic life. These hypoxic zones have been associated with the flow of water from various large rivers such as the Mississippi, the Atchafalaya River, and others. Temperature usually varies with water depth. Some species of saltwater fish need warmer water for example in winter months. Another problem that exists with fish farming or mariculture in the Gulf of Mexico is the existence of frequent thunderstorms that generate high winds and heavy seas. These thunderstorms can be an almost daily occurrence in the summer months. They occur with very little warning and can generate high winds and seas of 8-10 feet or more. Such seas are potentially destructive to any type of pen or cage that is used to contain fish as part of a mariculture operation.
If a fish pen or cage is of a substantial size, it requires substantial anchorage to support it in a desired position. This is another problem that plagues the concept of mariculture in the Gulf of Mexico. The seabed in the Gulf of Mexico is soft mud, and it is weak structurally. Therefore, the anchorage of substantial fish pens or cages is a problem considering the unconsolidated nature of the seabed.
Many mariculture and aquaculture systems have been patented wherein cages or pens are provided in a marine environment.
A lobster cage arrangement is seen in the MacDonald U.S. Pat. No. 3,499,421. The patent discloses the use of a plurality of piling driven into a seabed to support cages.
The Gollott U.S. Pat. No. 4,266,509 discloses an offshore habitat for shellfish. The apparatus includes an open framework enclosure and defines a plurality of laterally spaced side by side sets of vertically spaced elongated horizontal cavities open at one set of corresponding ends. At least one open top tray is slidingly removably received in each of the cavities through the open ends thereof and the upper portions of corresponding adjacent cavities of adjacent sets of cavities are horizontally communicated and the upper and lower portions of adjacent vertically spaced cavities are in direct communication with each other. The trays include foraminated bottom, side and end walls and the enclosure defines structure for preventing movement of the trays between corresponding laterally spaced cavities, outwardly of the remote sides of the endmost cavities and outwardly from the ends of the cavities remote from the open ends thereof. Further, structure is provided for releasably lockingly retaining the trays within the enclosure against removal from the open ends of the cavities and the trays are sufficiently closely vertically spaced to prevent natural shellfish predators from entering the trays.
A modular cage system for underwater use is disclosed in the Mickelsen U.S. Pat. No. 4,337,727. A vertical housing and feeding structure is provided for raising mariculture and other underwater animals. Tiers of feeding tubes, each of a successively longer length, form a backbone structure to which cages may be selectively connected. Each cage is connected along a vertical front face of the backbone structure so that one of the feeding tubes terminates at a point accessible from within the cage. A feed opening just above this termination point directs food material dropped through the feeding tube to either fall within the cage or be accessible from therewithin so that it may be consumed by the caged animal. All of the feeding tubes of each tier have a top open end that is positioned near the surface of the water to facilitate the controlled delivery of food to each individual cage. Two sets of backbone structure may be joined back-to-back so that cages may be connected to both sides of the structure, thereby doubling the cage capacity of the system. The capacity of the backbone structure may also be augmented by increasing the width of the tiers of feeding tubes or by adding additional tiers of feeding tubes to the back of each bone structure, each additional tier being of a successively longer length. Either method thus increases the frontal area of the backbone structure and provides additional frontal space to which additional cages may be attached. Inspection of the cages is facilitated by hoisting the entire backbone structure, including the cages attached thereto, out of the water. The walls of the cages are screened with a sufficiently large mesh to allow oxygenated water to freely circulate therethrough and to further allow fecal material and uneaten food to fall out of the cage without accumulation.
The Bourdon U.S. Pat. No. 4,716,854 provides an open sea aquaculture installation that comprises a central structure similar to an offshore drilling platform and several floating modules which are anchored to the seabed. The different modules are disposed at a distance, determined perpendicularly between lines each crossing a module and parallel to the mean direction of current in the surface layer of the sea, sufficient so that dejecta from the different modules do not interfere with adjacent modules.
An aquatic net pen and method is disclosed in U.S. Pat. No. 4,982,697. The pen has a light weight inexpensive net cover for the top which keeps predators out. The cover is easy to apply and remove and yet is held securely in place by means of studs or posts extending upwardly from the frame of the cage or pen and having enlarged heads which preferably are slightly larger than the holes in the mesh. Preferably the mesh is made up of resilient plastic strands which snap back into tier original shape after being deformed by the bolt-heads passing through, so that the bolt heads and the netting together form a snap-fitting fastening system. In one embodiment, panels of materials such plastic netting are suspended in cages so as to attract the growth of algae thereon for feeding algae-eating aquatic animals such as conch, fish, etc. in the cages. The panels are formed into a removable unit so that some of the units can be suspended in water elsewhere and transferred to the cage to replace units from which the algae has been depleted, thus feeding the aquatic animals by merely replacing algae-depleted units with algae-loaded units.
Various foreign patents have issued which relate to underwater farming of marine animals. A French Patent 2627-951-A concerns an underwater farm for the study of marine life. The farm consists of four (4) concrete blocks which are mounted on a metal frame that is anchored to the seabed. Each concrete block is formed with a large number of holes and recesses to provide shelter for small fishes from predators. The blocks also provide a base for the growth of marine vegetation. The blocks are connected to a research station on the shore by means of a pipe or umbilical cord, through which suitable food can be pumped to the blocks. An underwater television camera enables the marine animals to be observed from the shore station.
A Russian Patent SU 1405-747-A discloses a growing plant for sea organisms. The apparatus includes vertical supports arranged in two parallel rows and a supporting element with frame is located between the supports. The supporting element located between rows of supports carries a trust. Servicing of a fish crib is performed using two cranes with carriages. The system claims an advantage of easier maintaining of the plant with possible arrangement of larger numbers of fish cribs in the sea and simplified servicing.
It has been known in the art to convert oil rigs to fish habitat by toppling the rigs after they are abandoned. This concept was reported for example in the Washington Post Sep. 4, 1993 in an article entitled "Oil Rigs Convert to Fish Condominiums". The September, 1993 Washington Post article discloses that very large offshore oil platforms (for example 300 plus feet long) create an artificial reef for marine life when the oil production platform is turned on its side and sunk in the gulf of Mexico.